Immunocompetence and vigorous immune responsiveness are recognized as associated with a good prognosis when measured before surgery and before and after chemotherapy for cancer. Newer knowledge regarding the cellular and humoral divisions of the immune response make it possible to explore these immunological phenomena in greater depth and determine their etiology as well as their possible causal relationship to the clinical changes. We herein propose a multifaceted and serial approach to the study of immunocompetence and prognosis in surgical and chemotherapy treated patients with leukemia, lymphoma and solid tumors. In addition to lymphocyte blastogenesis and delayed hypersensitivity skin tests, the following tests will be done serially in patients undergoing cancer surgery or chemotherapy: migration inhibitory factor generation, blastogenic factor generation, enumeration of immunoglobulin receptor lymphocytes, complement receptor lymphocytes (B-cells), erythrocyte rosette forming lymphocytes (T-cells) and macrophage activity levels. These data will be used to develop and calculate an immunological index which will be used to correlate the immunological with the clinical findings. The data will reveal which immunological parameter or parameters correlate best with prognosis, which comes first, immunological or clinical change, the immunological effects of various types of therapy and the ideal periods for immunotherapy as well as the ideal associated therapy (that which augments cell mediated immunity). The data will hopefully also reveal the etiology of the cancer associated immunodeficiency.